A typical loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles, such as trucks and trailers. To compensate for height differences between the loading dock platform and an adjacent bed of a truck or trailer, many loading docks have a dock leveler. A typical dock leveler includes a deck or ramp that is pivotally hinged along a rear edge to vary the height of a front edge of the deck. An extension plate or lip extends outward from the front edge of the deck to span a gap between a rear of a truck bed and the front edge of the deck. This allows personnel and material handling equipment to readily move on and off the vehicle during loading and unloading operations.
The deck is usually moveable between a stored position and an operative position. Depending on the style of dock leveler, the deck may store either vertically or horizontally. Vertically storing decks are usually driven by a hydraulic cylinder. The hydraulic cylinder typically extends to raise the deck to a vertically stored position and retracts as the deck descends to an operative position. The force for lowering the deck can be provided from the hydraulic action within the cylinder and/or the weight of the deck itself. In some cases, the weight of the deck urges the deck downward while a hydraulic flow restriction associated with the cylinder provides the deck with a controlled descent.
Vertically storing dock leveler offer important benefits over horizontal levelers. They offer better access to a pit floor for cleaning, which may be required in some industries. In addition, vertically storing dock levelers facilitate an environmental seal between the outside dock door and the dock floor.